Nearly all electromechanical equipment becomes anomalously warm before it fails, making infrared (IR) cameras extremely effective diagnostic tools in the manufacturing environment.
Inspections using IR cameras can find many problems before failure occurs. In many cases the time to failure can be projected, enabling the most convenient scheduling of proactive, or preemptive, repairs. This practice, called predictive maintenance (PdM), enhances both productivity and safety.
IR cameras play a major role in PdM programs in manufacturing plants, electric power transmission and distribution systems, chemical plants, paper mills and numerous other industrial operations.
IR cameras are also ideal for monitoring objects and materials that present diagnostic thermal profiles, such as electricity transmission and distribution systems, materials in containment vessels and pipelines, materials and associated equipment during the manufacturing process, and breaches in security.
Other well-regarded inspection tools include human senses, vibration analysis, oil analysis (tribology) and ultrasound analysis. However, IR thermal inspections are accurate, rational, intuitively interpretable, nondestructive, noninvasive, noncontact and fast. They provide instant images and data that are immediately useable in reports, and can be easily archived to enable a trending study of performance.
This in turn may be used to project time-to-failure, enabling optimal scheduling of maintenance based on actual operating condition, and preemption of catastrophic failure.
Infrared technology has been used at the General Motors Powertrain Engine Facility in Romulus, Mich. on a full-time basis since 1988 as part of the predictive maintenance program. IR inspections add real value to the facility’s total predictive/preventive maintenance program. Personnel continually inspect electrical components - including the aging electrical bus, all mechanical equipment, and the building envelope including the roof.
The Romulus Engine plant was recognized for the fourth consecutive year as the most productive 8-cylinder engine plant in North America by the authoritative Harbour Report. The plant achieved a production rate of 3.49 hours per engine, a 3.6 percent improvement over last year. Overall, GM Engine operations continued to lead the domestic car companies with a 5.2 percent improvement over last year.1
Through a corporate initiative, the GM Infrared Standards Committee continually tracks the value of this program on the basis of a written cost avoidance calculation and procedure. As a result of continued, demonstrated savings, GM has adopted the Powertrain Engine Facility’s written practice, which it treats as a living document and continually encourages input from the members of the GM Infrared Users Group.
Following are three recent case studies at the Romulus facility in which inspection of equipment using infrared cameras has yielded significant savings.
Figure 1. The GM V-8 assembly process at the
Romulus Powertrain Engine Facility terminates
with an extensive, 15-mile long conveyor system
that automatically sorts finished engines
for shipment. Dan Sinclair uses an IR camera
to check the condition of the rollers and the chain.
Engine Delivery System Turns
The V-8 engine assembly process is terminated on a “power and free system” in which the finished engines are marshaled and sorted for shipment by automated equipment. Within the system, many dips and turns have been incorporated to facilitate the 15 miles of chain needed to accomplish this task.
Turn roller failure (Figures 2 and 3) and an overheated chain (Figures 4 through 8) were two recent problems that were resolved with proactive repairs. These repairs eliminated the major downtime that could have occurred if the turn rollers were allowed to run to failure, which would have necessitated more costly and time-consuming reactive repairs.
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Figure 3
Case Study No. 1: Turn Roller Failure
Figure 2. During a walk-through inspection, an anomaly was spotted thermally (right) and visually (left) in a roller in this turn.
Figure 3. Upon closer inspection, the IR camera pinpoints the actual failed roller, which has an anomalously warm temperature of 103.9°F. Photo at left shows the roller close-up.
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Figure 4
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Figure 5
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Case Study No. 2: Overheated Chain
While examining the west chain on the V-8 engine track (Figures 4 and 5), it was noticed that the west chain was about 10°F warmer than the east chain (Figures 6 and 7). An elevated temperature indicates friction, which causes wear and increased electrical load. After a short investigation, an empty automatic grease system (Figure 8) was identified as the culprit and promptly refreshed.
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Figure 6
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Figure 7
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Figure 8
Case Study No. 3: Overheated Bearing
Large cutters with precision bearings, such as the one shown in Figures 9 through 12, are employed on one of the transfer machines. The IR camera immediately revealed an abnormal heating pattern consistent with failed bearings. Upon further examination, the machine repair crew found that an oil seal had failed and allowed the machine cutting fluid to contaminate the bearing lubrication.
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Figure 9
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Figure 10
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Figure 11
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Figure 12
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Proactive Repairs Avoid Major Reactive Repair Costs
The success of any preventive maintenance program is measured by comparing the costs that are avoided by early, proactive detection and optimal scheduling of repairs versus the costs of making reactive repairs after a failure or breakdown occurs. Proactive repairs make the same common sense as locking the proverbial barn door before, rather than after, the horses are gone!
The Romulus engine plant has a formal cost avoidance worksheet for proactive repairs, which includes:
- A statement of the root cause for action - a description of the imminent problem
- A description of the proactive repair performed
- An analysis of the costs of the actual proactive repair task
- An analysis of the projected costs of the reactive task that was preempted
By comparing the costs of the proactive task with the projected costs of the reactive task, the value of the preemptive repair is determined. While some cost factors may remain unchanged in both cases, for example, replacement of worn-out and broken parts, three major benefits can be realized by proactivity. First, repairs can be scheduled during convenient times such as during shift changes or during planned downtime.
Second, the collateral effects of actual failure are avoided, such as additional damages, production losses and worker safety issues. Third, the time required to make proactive repairs is likely to be substantially shorter than reactive repairs, further minimizing or eliminating lost production. Following are analyses of the costs avoided in two actual examples of proactive repair.
Example No. 1: Overheated Chain on V-8 Engine Track (Case Study No. 2)
The cost of proactive repairs to the overheated chain included $45 for one man-hour of labor plus $20 for grease. The projected reactive task costs that would have accrued had the chain been run to failure were: 136 hours of repair labor at $45 per hour, plus 1,072 hours of lost production labor at $39 per hour. The parts costs of $32,430 to replace 4,600 links of chain, plus $750 for new drive chains and $20 for grease, must also be added to the costs.
The avoided costs were clearly substantial. The total cost of the proactive repair was a mere $65, but the total reactive repair would have cost $81,078, plus the unquantified cost of lost production for two shifts, an estimated 2,100 V-8 engine units, for a total savings in the range of $1 million!
Example No. 2: Anomalously Hot Feeder Bus Isolation Switch
IR inspection revealed that a feeder bus isolation switch on the north side of the plant was emitting a heat signature consistent with a high-resistance connection. The switch was shut down, locking out the bus supply. The feeder bus was disconnected from the switch, the bus bars were cleaned, bus insulators were replaced, and bus power was reset without incident.
The cost of this proactive repair was $1,080 for 24 man-hours of repair labor at $45 per hour and $590 for replacement bus insulators, a total of only $1,670. If the situation had been ignored and the equipment run until failure, the reactive repair costs would have totaled $41,977, the sum of 156 hours of repair labor at $45 per hour, 672 hours of lost production labor at $39 per hour, and $8,749 for parts, including replacement bus insulators, a section of bus, a new bus isolation switch, temporary service wire, a 1,000-amp temporary bus plug and a 1,000-amp fuse.
The savings totaled $40,307, plus the avoided costs of ripple effects throughout the section of plant crippled by the resulting unplanned power outage. These avoided costs would include the cost to recover machine programs, cost of cutters and tooling destroyed due to in-cycle power failure, and the significant but incalculable cost of in-process engine blocks that would have to be scrapped due to tooling failure.
An Ounce of PdM Prevention is Worth a Ton of Cure
Thermal cameras are used throughout GM plants. They record both high-resolution IR and visual images as well as text and voice recordings in onboard RAM, can record thermal video, support a broad family of interchangeable lenses, and offer numerous time-saving automated performance features. Dramatic savings are achievable from regular preventive and predictive maintenance in large manufacturing facilities, based on detection of incipient failures by IR thermal inspections and other test methods. There are three main reasons for the savings:
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First, repairs are much cheaper to make before catastrophic failure occurs. Such proactive repairs avoid collateral damage to other equipment, in-process product and even personnel.
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Second, repairs can often be made during scheduled downtime or during shift changes, minimizing or eliminating lost production.
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Third, the time required to make proactive repairs is likely to be substantially shorter than reactive repairs, further minimizing or eliminating lost production.
The dollar value of proactive savings has traditionally been difficult to certify, but modern smart IR cameras (Figure 13) and other computer-friendly test equipment are greatly facilitating record-keeping by downloading data to easily analyzed digital archives.
Figure 13
In addition, report-generating and data-archiving software are greatly facilitating the quantification of proactive repairs at GM.
The result is an ongoing paradigm shift by enlightened plant management. The plant maintenance paradigm is moving from the cost side of the ledger, where it has traditionally been considered overhead maintenance and operation (M&O) costs, to the nascent category of avoided costs.
This shift is in turn recasting maintenance professionals and PdM programs as part of the profit-making side of today’s manufacturing organizations. Indeed, a dollar saved has always had the same value as a dollar earned. In a highly competitive global industry such as automobile manufacturing, the true value of avoided costs produced by today’s predictive/preventive maintenance professionals is realized on the income side of the ledger, and can be expressed in terms of dollars-worth of increased productivity, lower manufacturing costs and larger margins.
References
- Romulus Engine Newsline, June 10, 2004.
- Harbour Consulting. The Harbour Report North America 2004. Troy, Mich. June 10, 2004.
